1. Field of the Invention
The present invention relates to a backlight unit. More particularly, the present invention relates to a backlight unit in which an incident surface of a light-guiding plate is formed in a shape of a curve, or a curve-shaped structure is formed in a housing to improve the light efficiency.
2. Discussion of the Related Art
Among the various ultra-thin, flat type display devices, which include a display screen having a thickness of several centimeters, a liquid crystal display (LCD) device can be widely used for notebook computers, monitors, aircraft, and etc.
Unlike other flat type display devices, the LCD device can not emit light by itself. In this respect, the LCD device requires a backlight unit provided in the rear of an LCD panel, wherein the backlight unit is used as a light source for the LCD device.
The backlight unit may be classified as a direct type or an edge type.
In a case of the direct type backlight unit, a plurality of lamps are arranged at an entire lower surface of an LCD panel, whereby light is directly transmitted to the LCD panel. In the edge type backlight unit, a lamp is formed in one lower edge of an LCD panel, and light is transmitted to the LCD panel by a light-guiding plate.
Hereinafter, a related art edge type backlight unit will be described with reference to the accompanying drawings.
FIG. 1 is a cross sectional view of a related art edge type backlight unit. As shown in FIG. 1, the related art edge type backlight unit includes a lamp 10, a housing 20, a light-guiding plate 30, and a reflective sheet 40. At this time, the lamp 10 is provided at one lower edge of an LCD panel (not shown) to emit the light. Also, the housing 20, surrounding the lamp 10, protects and supports the lamp 10. The light-guiding plate 30 is formed below the LCD panel, wherein one side of the light-guiding plate 30 is opposite to the lamp 10. Thus, the light-guiding plate 30 guides light emitted from the lamp 10 to the LCD panel. Then, the reflective sheet 40 is formed under the light-guiding plate 30 to reflect the light leaking in an opposite side of the LCD panel to the light-guiding plate 30.
Although not shown, optical sheets, such as a diffusion sheet; a prism sheet and a protective sheet, are provided on the light-guiding plate 20, whereby the light guided by the light-guiding plate is uniformly diffused to the LCD panel. Also, the lamp 10, the housing 20, the light-guiding plate 30, the reflective sheet 40, and the optical sheets are taken into a main support 50.
An operation of the related art edge type backlight unit will be described as follows.
First, the light emitted from the lamp 10 may be incident on the incident surface of the light-guiding plate 30. In another way, the light emitted from the lamp 10 is reflected on the housing 20 surrounding the lamp 10, and then the reflected light is incident on the incident surface of the light-guiding plate 30.
Some of the incident light is directly reflected to the upper surface of the light-guiding plate 30. Also, some of the incident light leaks out to the lower side of the light-guiding plate 30, and then the light is reflected by the reflective sheet 40 and is sent to the LCD panel.
The light guided by the light-guiding plate 30 is incident on the LCD panel through the optical sheets, wherein the optical sheets are comprised of the diffusion sheet, the prism sheet, and the protective sheet. At this time, the diffusion sheet serves to uniformly diffuse the light guided by the light-guiding plate 30 to the LCD panel. Also, the prism sheet serves to guide the light vertically. The protective sheet is provided on the prism sheet to protect protruding and recess patterns formed in the prism sheet.
Thus, the light emitted from the backlight unit is transmitted to the LCD panel, thereby displaying images. In the total amount of energy for operating the LCD device, a considerable amount of energy is used in the backlight unit. In this respect, it is necessary to improve the light efficiency of backlight unit so as to improve the light efficiency of the LCD device.
However, the related art backlight unit has the following disadvantages.
When the light is emitted from the lamp 10 of the backlight unit, the lamp 10 absorbs the light. Also, the housing 20 surrounding the lamp 10 absorbs the light, thereby lowering the light efficiency. Accordingly, there have been demands for a backlight unit that can obtain high light efficiency.